Effect of the previous crop on cortical cell number of Malus domestica cv. Starking Delicious apple flower primordia, flowers and fruit

Abstract

The effect of the crop of the previous season on cell size of the cortical region of flower primordia, flowers and fruit size in Starking Delicious apples was investigated. Cell number was monitored from the onset of differentiation of the sepal primordia of terminal flowers until maturity. A heavy crop during the previous season resulted in a decrease in cell number of the cortical tissue at the base of the developing flowers and fruit, and in reduced fruit size. The reduction in cell number was already evident eight weeks after the onset of differentiation of the sepal primordia. Although a decrease in the cell numbers of fruit was accompanied by large cells, these larger cells did not compensate for the reduction in cell numbers as determined by fruit size. The effect of crop size on fruit size persisted during the following two seasons notwithstanding thinning practices aimed at normalizing cropping levels. Lower cell numbers were evident when fruit of similar sizes were compared.